There is growing recognition that informal summer conferences which bring together investigators in related areas of study provide unique opportunities to develop new lines for research. The Gordon Conferences have provided such a format. These meetings facilitate interchange at formal and informal sessions in settings where distractions can be kept to a minimum. The Gordon Conference program, however, cannot cover all the topics of interest to members of FASEB. For this reason FASEB has initiated a series of summer conferences which follows the format of the Gordon Conferences. This year the FASEB Research Conference Committee has identified The Development and Senescence of the Immune System as a timely subject for a conference. No recent conference has brought together immunologists with interest in the development and senescence of the immune response. The reorganization of DNA during the development of lymphocytes, the existence of distinct cell surface determinants which mark stages of differentiation and the regulatory interactions among various cells of the immune system provide the basis for new understanding of the immune system. There is little doubt that new understanding of the immune system will lead to fresh insights into diseases including cancer, congenital and acquired immune deficiency which now trouble our society. Nine of the world's leading immunologists have agreed to lead sessions and their participation assures the high scientific level of the meeting. The modest fee (approximately $300) for registration, room and board should permit students and young investigators to attend the conference. Nine major sessions will be held with approximately 30 invited speakers and 120 other participants. While the invited speakers set themes for the meeting, poster sessions and the considerable time allocated to discussion permit each attendee to participate fully.